IP is one of many protocols on the Internet. Its role is to deliver data in packets to and from Internet-connected computers, which are identified with an IP address. Splitting the data up in packets allows them to take many different routes to computers. This is an intentional design feature of the Internet, which allows it to survive partial large-scale network outages. Unfortunately, the free routing across all hosts on the Internet is no longer done, as the networks have become commercialised and charge for traffic.
Currently, the Internet is built around IP version 4, but the more feature-rich IP version 6 is starting to appear on experimental networks.